Brake apparatus



Jan. 16, 1934. E. G. CARROLL 1,943,886

BRAKE AYPARATUS Filed Oct. 29, 1928 2 Sheets-Sheet l lM/ENTQRI Jan. 16,1934.

E. G. cARRoLL BRAKE APPARATUS Filed Oct. 29. 1928 2 Sheets-Sheet 2 I NVEN TOR.

Patented Jan. 16, 1934 UNITED STATES PATENT OFFICE BRAKE APPARATUSEugene G. Carroll, Los Angeles, Calif., assignor, by mesne assignments,to Bendix Brake Company, South Bend, Ind., a corporation of IllinoisApplication October 29, 1928. Serial No. 315,630

32 Claims.

ever, the invention is particularly useful when applied for actuatingduid-actuated brakes, such as used in an automobile. Althoughtheinvention can be used where the operating fluid is compressed air, inthe present specicationit is del@ scribed as applied to a hydraulicbrake apparatus.

In the use of hydraulic brake apparatus, diniculty is experienced onaccount of leakage, and also, sometimes there is a tendency for air to'accumulate in the system in such a way as to interfere with thereliable operationof the brakes. In such apparatus a. master cylinder isusually employed in which thel uid is compressed by a foot pedalthatvoperates a plunger in the cylinder.

In order to insure a suilicient supply of operating fluid, somehydraulic brake apparatus in- Qcludes a reservoir maintained incommunication with the master cylinder through a port in the cylinderwhen the plunger is in its withdrawn position. .In using such areservoir, however,

there is a tendency to produce a retarded development ofthe operatingpressure ahead of the plunger due to the fact that the operating liquidescapes through this port connection until it becomes closed. In otherwords, there is a tend- .30 ency to retard the development of theoperating pressure on account of the presence of this port.

'I'he use of cylinders heretofore has necessitated the provision ofsmooth bores in the cylinders in order to insure fluid-tight operationof the pistons or plungers that operate in the bres.

The general object of this invention is to overcome these difculties andto provide a simple fluid pressure apparatus which will be reliable inoperation and which will operate to develop the 40 required pressure atan early point in the forward movement of the plunger that develops thepressure. As applied to a hydraulic brake apparatus, the general objectof the invention is to provide simple apparatus for this purpose, conystructed in such a way as to avoid leakage from the system, and so as toinsure an ample supply ofthe operating liquid to the master cylinder andbrake cylinders.

A further object of the invention is to construct the apparatus in suchaway that a relatively higher pressure is developed in the rear` brakecylinders as compared with the forward brake cylinders, the purposebeing to develop a relatively smaller braking action on the forwardwheels, which is desirable.

' a plane at right angles to the axis of rotation of withdrawn positionof the plunger, this chamber A further object of the invention is toprovide a construction for the master cylinder whichwill have the effectof automatically building up a pressure above atmosphere in the systemand which will operate to boost or supercharge the 6l) pressure in thebrake cylinders immediately when the plunger commences to advance.

A further object of the invention is to limprove the generalconstruction of fluid-actuated pressure apparatus, and also to improvethe construction of master cylinders and brake cylinders.

Further objects of the invention will appear hereinafter.

The invention consists in the novel parts and combination of parts to bedescribed hereinafter, all of which contribute to produce an efficientbrake apparatus.

A preferred embodiment of the invention is described in the followingspecication, while the broad scope of the invention is pointed out inthe appended claims.

In the drawings:

Figure 1 is a vertical section through a brake apparatus embodying myinvention and taken in the wheel or drum to which the brake is applied.Figure 2 is a section taken on the line 2-2 o Figure l. Figure 3 is avertical section illustrating the master cylinder and a pressurereservoir which may be employed with it, certain parts being brokenaway.

Before proceedingto a detailed description of the invention, it willfacilitate the disclosure to state that according to my invention, inthe construction of the master cylinder I provide a plunger having ahead workingy in a booster chamber or bore connected with a reservoirfor the operating fluid or liquid. In the normal, or

is inV communication with another chamber in Awhich the pressure isdeveloped to serve the brake cylinders or other devices served by theapparatus. When the plunger is advanced, the immediate effect of theadvance is to increase the pressure in thel reservoir and in the boostercylinder associated with the apparatus. After a slight movement of theplunger has taken place, the actuating cylinder is cut off fromcommunication with the first cylinder to enable the actuating pressureto be developed. In this way, there can be no loss of pressure in theactuating cylinder when the plunger commences to move, in fact, anincrease of pressure commences in both cylinders or chambers immediatelywhen 31( the plunger begins its advance. In other words, I provide whatmight be called a booster cylinder co-operating with the regularcompression cylinder or chamber of the master cylinder, the effect ofthe booster cylinder being to increase the pressure in the regularcompression cylinder and maintain a plentiful supply of the operatingliquid for it. When communication of the supply liquid to thecompression cylinder is cut on", the actuating pressure is immediatelydeveloped in the compression cylinder.

The pressure reservoir employed in connection with the system is notcompletely filled with the operating liquid when used with a hydraulicsystem, and this reservoir is so constructed that an 'air chambercontaining compressed air exists in the reservoir. The immediate effectof the rst part of the forward movement of the plunger is to raise thelevel of the liquid in this reservoir and increase the pressure in it.

In brake apparatus where the forward brakes are served by a diiferentcylinder from that which serves the rear brakes, I utilize this increasein pressure in the reservoir to supercharge or increase the pressure inthe cylinder that supplies the liquid to the forward brakes. In this wayI insure a plentiful supply of the operating liquid to both sets ofbrakes.

In hydraulic brake apparatus it has been customary in the past to employa plunger having a head with suitable packing moving in a smooth bore ofa cylinder. In practicing my invention this is unnecessary, and Iprovide a construction' for the compressing cylinders that avoids thenecessity for using a piston with a head filling the bore of thecylinder. The plunger is inthe form of a headless .plunger or bar thatdoes not touch the bore of the cylinder, but merely slides through a xedhead of the cylinder, where it can be very readily packed, and developspressure simply by reducing the effective volume of the cylinder. Iemploy this construction for the compression cylinders or bores of themaster cylinder, and also for the brake cylinders.

In the preferred embodiment of the invention, I provide a compressioncylinder corresponding to the rear brakes and a separate compressioncylinder corresponding to the forward brakes. This arrangement isdesirable because if any accident occurs to the rear brake system, theforward brake system may still be employed, and vice versa. In thepreferred embodiment of the invention these two compression cylindersare placed in tandem with each other, and the plunger which operates inthe compression cylinder for the rear brakes is connected with a smallerplunger that operates in the compression cylinder for the forwardbrakes. Between these two plungers I prefer to provide a yieldingconnection that in operation will develop a slightly less pressure inthe forward compression cylinder, thereby insuring that the forwardbrakes will be applied less forcibly than the rear brakes.

In practicing the invention as applied to a hydraulic brake apparatus, Iprovide a brake cylinder with a chamber within it to receive theactuating fluid under pressure. According to my invention it is notnecessary to provide a bore within the cylinder for the plunger and I donot employ any head on the plunger, guided on the cylinder wall. It istherefore unnecessary to provide packing between the plunger and thecylinder wall, which packing heretofore has been generally used inpractice. It has the disadvantage that if it permits leakage, itdetracts from the holding power of the brake. According to my invention,I provide the end of the cylinder with a head having a bore through it,and this bore operates as a guide for the plunger, the inner end ofwhich is disposed within the pressure chamber of the cylinder.

I provide packing for the plunger where it slides through the head. Thehead is detachably mounted in the end of the cylinder so that whendesired it can be removed to repack the plunger. The packing is locatedon the inner end of the head around the plunger and the pressure on theinterior of the cylinder assists in holding the packing tight around theplunger.

In the embodiment of the invention illustrated in Figures 1 and 2, 1represents a brake housing in the form of a disc having a flange 2around its edge. This flange laps over a flange 3 on a disc 4 that isattached to the wheel 5 or other part to which the brake is to beapplied. This type of brake illustrated is a drum type of brake such asordinarily used in automobiles. The brake is an inside expanding brakeand is formed of two brake sections or shoes of arcuate form attached toa common pivot pin or anchor 7 on the housing, and provided with brakeliners 8 on their outer faces to engage with the inner face of the drumflange 3.

On the inner face of the housing I attach a brake cylinder 9 and thiscylinder has a chamber 10 on its interior to receive Iactuating fluidthrough a pipe connection 11 communicating with a port 12 leadingthrough the bracket 13 of the cylinder into the chamber 10. 'Thisbracket 13 may be attached to the housing 1 by means of bolts 14. 'Thecylinder 9 in the present instance is a double ended cylinder, that isto say, it has a working plunger at each end. In the present instance,this cylinder is of V form, so that it consists of two sections 15 and16 cast integral with each other,

the axis of each section forming an obtuse angleV with the axis of theother section.

Each end'of the cylinder 9 is provided with a detachable head 17. Theseheads are preferably secured in place by means of a thread connection18. Each head 17 has a bore 19 through it which operates as a guide fora plunger 20. These plungers do not engage the'bore of the cylinder 9but their inner ends extend into the chamber 10, so as to come under theinfluence of the uid pressure existing therein.

The inner end of each head 17 is formed with 'a reduced extension 21around which a packingring 22 is placed. This packing-ring has a portionthat extends into the annular space 23 between the extension 2l and thewall of the cylinder 9, and its body seats on the end of the extension21. With this arrangement for the packing, it will be evident that thepressure developed within the chamber 10 will tend to press the packingclosely around the plunger 20 and pack it at the point where it passesthrough the head 17.

In order to impart braking movement to the brake sections 6, eachplunger is connected with the free end of the brake section, that is tosay, the end remote from the anchor or pivot. For this purpose, eachplunger is provided at its outer end with a deep recess 24 and receivesthe inner end of an adjustable strut-link. Each strut-link has a roundedhead 25 that seats in the rounded inner end of the recess 24. Thestrut-link includes an adjustable section 26 in the form of an eyebolt,the eye of which is attached by a pivot pin tion.

.tti

The brake sections are held off or out of contact with the brake drum bycoil springs 29, the inner ends of which are attached to lugs cast onthe cylinder 9, and the outer ends of which are hooked into thecorresponding brake section. These springs hold the brake sections upagainst stop pins 30 that project in from the side of the housing.

In the operation-of the brake, when the pressure is developed in thechamber 10, the plungers will be forced outwardly and this will move thebrake shoes or sections 6 outwardly inner face 0f the drum.

It desired, the upper side of the cylinder 9 may be provided with athreaded opening 31 closed by a removable screw 32. This removable screwwill give access to the interior of the cylinder without necessitatingtaking out the heads 19. By disconnecting the pin 28 of either of theeyebolts 26, the eye-bolt can be slightly rotated in either direction toadjust the length of the strutlink of which it forms a part. Thisenables the position of the brake shoe to be adjusted with respect tothe face of the drum.

Referring to Figure 3, 33 represents a master cylinder, one end of whichis formed into a booster cylinder 34 having a chamber or bore 35 ofrelatively large diameter. In tandem with this booster cylinder 34, Iprovide a compression cylinder 36, having a chamber or bore 37 with aconnection 33 leading to the rear brakes of the car, in case the systemis to be used where separate cylinders are provided for the forward andrear brakes.

Connected in tandem with the compression cylinder 36, I provide asmaller compression cylinder 39 having a relatively small chamber orbore 40, and this chamber is connected by a connection 41 with theforward brakes. The outer end of the cylinder 40 may be closed by ascrew plug 42. In the present instance I provide a xed headv43separating the booster chamber 35 from the compression chamber or bore37 which lis of vrelatively smallerl diameter than the bore 35.

This fixed head may be in the form of a plug screwed into the end of thebore 37, and provided with sockets 44 for a Spanner wrench. This head 43is practically a bushing having a bore 45 through it to guide a plunger46 inthe form of a cylindrical bar, the outer end of the said plungerbeing provided with a head 47 sliding in the bore 35. The inner end ofthe head or bushing 43 is provided with a packing-ring 48 that packsagainst the side face of the plunger 46, The head 47 of the plunger 46may be packedv in any suitable manner, for example, by means of a cupleather 49 held against the inner face of the piston by a coil spring50. This spring will be referred to hereinafter.

A4 somewhat similar construction is employed for connecting the chambers37 and 40, including `a xed head 51 which has a thread connection oneach side with the cylinders -which it connects. Through this xed head51 a plunger 52 slides,

said' plunger being of smaller diameter than the plunger 46 and beingconnected with theplunger 46 in such a waythat when the plunger 46 isadvanced in the operating movement, the plunger 52 will also advance,thereby compressing uid in the chamber 40. The connection between theplungers -is preferably a yielding connection including a coil spring 53that seats against one end of the plunger' 46 and at its other endagainst a screw cap 54 attached to the end of the plunger 52. A bolt 55extends through the cap 54 and against the i ward brakes than in therear brakes.

is secured in the end of the plunger 46 to limit the distance that theplungers 46 and 52 can be moved apart. In other words, the spring 53 isin compression and holds the cap 54 against the face of the head 56 ofthe bolt. The bolt-head 86 56 is received loosely in a chamber 57 in theend of the plunger which provides clearance permitting considerablemovement of the bolt-head 56 in the direction of the bore 40. The resultof this is that when the plunger 46 moves toward 85 the right the forcethat moves the plunger 52 is imparted to it through theV spring 53. Thisspring is of such strength that it will yield slightly when the plungersare moved, thereby imparting a reduced amount of movement to the plunger52 90 and thereby developing less pressure in the for- In case the rearbrake system is out of order and not supplied with iluid under pressure,the plunger 46 can still operate the plunger 52 through the spring 53,and after compression of the spring v 53 suiciently, by the directcontact of the head 56 with the end face 58 of the plunger 52 whichforms one end of the chamber 57.

Any suitable means may be provided for operating the plunger 46. Inpractice, in a hydraulic brake apparatus, this is usually effected by abrake pedal, operating through an adjustable connection 59 including astern 60 with a rounded head 61 thrusting against" the end of theplunger and retained by a bushing 62 screwed into the end of theplunger.

I provide means for supplying ilud or liquid under pressure to thebooster cylinder 34 and to the chambers 37 and 40. to supply the chamber37 from the chamber 35 through a by-pass port or passage 63 which isassociated with the plunger 46 and preferably in the form of anelongated passage formed in the face of the head 43 and communicating115 through a port 64a in the plunger with a counter-bore 64 in the endof the plunger that is exposed to the interior of the chamberA 37, Ialso provide a pressure reservoir 65 which may be of dual form providingtwin containers 66 with a partition wall 67 separating the same,4 butpermtting communication if the level 68 of the operating liquid issufficiently high. One of the containers 66 is connected by a pipe 70with the chamber 35. A relatively small passage 70e is provided in thisconnection. The other container is connected by a pipe 69 with the xedhead 51, said head having a large radial passage 71 formed -in itexposed at its inner end to the side of the plunger 52.

Associated with the plunger 52, I provide a port which communicates withthe passage 71 in the withdrawn position of the plunger 52, asillustrated in Figure 3. For this purpose I provide a port 72 in theinner face of the head 51 which 135 communicates at its right endthrough a port 73a in the plunger with a counter-bore 73 in the end ofthe plunger and communicating with the interior of the third chamber 40.

At both points where the plunger 52 emerges 14() from the head 51, Iprovide suitable packingrings 74 that keep this plunger substantiallyhuid-tight.

In order to enable the system to operate witha pressure slightly higherthan atmosphere and 145 thereby insure that no partial vacuum will bedeveloped at any point in the system which rn'ght4 have the effect ofadmitting atmospheric air, l provide the upper end of the reservoir 65with an airtight head 75 held securely on a gasket 76. 150

I prefer, however, 13

In the operation o the system, the reservoir cannot be completely lledwith the liquid by reason of the fact that I provide the illing or inletopening 77 with a downwardly projecting sleeve 78. This sleeve preventsthe reservoir from being completely filled with the liquid because asthe level rises, Aan air pocket or chamber 79 will be formed under thehead.

The area o the plunger 52 is preferably onehalf of the area of theplunger 46. This correlation gives a desirable mode of operation in thatwhen the plungers move forward, there will be substantially the sameamount of liquid displaced from the chamber 37 as from the chamber 40.

In the operation of the master cylinder embodying the featuresdescribed, when the plunger 46 advances, fluid or liquid in the chamberwill be displaced by the advancing head 47. Some of this liquid willtend to flow through the port 63, further compressing the liquid alreadyAin the chamber 37, and some or the liquid will flow up the pipe 70,raising the level 68 of the liquid in the reservoir and furthercompressing the compressed air in the air pocket 79. This increase inpressure in the reservoir at this timeis desirable because it increasesthe pressure of the liquid in the pipe 69 and this communicates with theinterior of the chamber through the port 72, thereby increasing theinitial pressure in this chamber. This initial increase in pressurecaused by the booster cylinder in the chambers 37 and 40 immediatelyincreases the pressure in the brake cylinders and, one might say, setsthem in readiness for immediately applying the brakes upon the furthermovement of the plungers 46 and 52. As soon as the plunger moves to theright sumciently, it will close the port 63 at its right end, and-whenthis closes, all the liquid in the chamber 37 will be trapped thereinand the pressure will immediately rise in the connection 38 and in therear brake cylinders. to the right suiciently to close the right end ofthe port 72, the liquid in the chamber 40 will be trapped and thepressure will immediately rise therein and apply the brakes of theforward wheels.

The time of closing the port 63 can be very accurately determined bylengthening or shortening this port. If quick closing of the port isdesired, the portwould be made relatively short. This is also true ofthe port 72.

If the connection between the plungers 46 and 52 had no lost motion,such as illustrated, the same pressure would be developed in the forwardbrake cylinders as the rear brake cylinders, but by reason of the spring53 a slight compressionof the spring will take place in transmitting themovement from the plunger 46 to the plunger 52, and this will causeslightly less displacement of liquid in the chamber 40, thereby slightlyreducf ing the pressure in the forward brake cylinders as compared tothe pressure in the rear brake Y: cylinders.

Attention is called to the use of the xed heads 43 and y51. By employingthese heads I avoid the necessity for accurately boring the chambers ofthe cylinders 36 and 39, because their plungers do not come in contactwith the walls of these cylinders. This arrangement is also advantageousbecause it is much easier to make a liquid-tight connection between theplungers and the fixed heads than it is between a head moving in a boredcylinder.

Likewise, when the plunger 52 moves reaasec The principal function ofthe spring is to hold the cup 49 in position; also to act as aretraction spring to return the plunger 46 to its normal position afterit has been actuated.

By reason of the fact that the passage a is small, a choking eiectoccurs when the plunger 46 is actuated, immediately raising the pressurein the booster chamber 35 and communicating this pressure through theby-pass 63 and port 64 to the compression chamber 37. When the mastercylinder lirst commences to operate, on the return stroke of the plunger46, a partial vacuum will be developedY in the booster chamber 35 byreason of the restricted passage 70e. This operates to admit air pastthe head 47 and the cup ring 49. This air finds its way upv theconnection 70 and into the air chamber 79. In this way the operation ofthe master cylinder automatically develops air pressure in the airchamber 7 9.

It is understood that the embodiment of the invention described hereinis only one of the many embodiments this invention may take, and I donot Wish to be limited in the practice of the invention, nor in theclaims, to the particular normally holding the same in its withdrawnposition, said plunger having a port formed therein emerging on the sideface thereof opening communication between the booster cylinder and thecompression cylinder when the plunger is in its withdrawn position, saidport operating to` close when the plunger is moved forward to developpressure in the compression cylinder, and a connection from thecompression cylinder for delivering fluid under pressure from the same.

2. In fluid pressure apparatus, the combination of a cylinder having achamber of relatively large diameter and a chamber of relatively smallerdiameter, a plunger with a piston head lling the bore of the largerchamber, a fixed head separating the larger chamber from the smallerchamber and having a guide opening therethrough for the plunger, apassage for connecting the chambers, means for supplying operating iiuidto the chambers, said rst named chamber co-operating with its plunger toforce a portion of the operating uid through the passage into the secondnamed chamber at the commencement only of the yforward stroke of theplunger and a connection from the smaller chamber for delivering fluidunder pressure from the same.

3. In uid pressure apparatus, the combination of a cylinder having achamber of relatively large diameter and a chamber of relatively smallerdiameter, a plunger with a piston head filling the bore of the largerchamber, a xed head separat- 1 ing the larger chamber from the smallerchamber and having a guide opening therethrough for the plunger, saidplunger having a passage in its face connecting the two chambers whenthe plunger is in its withdrawn position, means for supplying i andhaving `a guide opening therethrough for the plunger, means forsupplying operating fluid to the larger chamber, a connection from thesmaller chamber for delivering the fluid under pressure from the same,means connected with the plunger for advancing it, means for returningthe plunger after it has'I been advanced and for normally holding thesame in a withdrawn position, and means for maintaining communicationbetween the two chambers when the plunger is in said withdrawn position.

5. In fluid pressure apparatus, the combination of a cylinder having achamber of relatively large diameter and a chamber of relatively smallerdiameter, a plunger with a piston head filling the bore of the largerchamber, a fixed head separating the larger chamber from the smallerchamber and having a guide opening therethrough for the plunger, meansfor supplying operating fluid to the larger chamber, a connection fromthe smaller chamber for delivering fluid under pressure from the same,means for forcing the plunger forward, means for returning,r the plungerand normally holding the same in its withdrawn position, and a passageassociated with the plunger for maintaining open communication betweenthe two chambers when the plunger is in its withdrawn position. l

6. In fluid pressure apparatus, the combination of a cylinder having achamber of relatively large diameter Aand a'chamber of relativelysmaller diameter, a plunger with a piston head filling the bore of the,larger chamber, a xed head separating the larger chamber from thesmaller chamber and having a guide opening therevthe plunger is in saidwithdrawn position, and operating to close as the plunger movesforwardly to develop pressure in the smaller chamber.

opening communication between said chambers 7. In uid pressureapparatus, the combination ofv a cylinder having a chamber of relativelylarge diameter and a chamber of relatively smaller diameter, a plungerwith a piston head filling the bore of the larger chamber, a fixed headseparating the larger chamber from the smaller chamber and having aguide opening therethrough for the plunger, means for supplyingoperating fluid to the larger chamber, a connection from the smallerchamber for delivering fluid under pressure from the same, means forforcing the plunger forward, means for returning the plunger and,normally holding the same in its withdrawn position, saidplungerhavinga port when the plunger is jin said withdrawn position, andoperating to close when the plunger is moved -forwardly to developpressure in the smaller chamber.

8. In fluid pressure apparatus, the combination of a cylinder having achamber of relatively large diameter and a chamber of relatively smallerdiameter, a plunger with a piston head filling the b'ore of the largerchamber, a fixed head separating the -e larger chamber from the smallerchamber and having a guide opening therethrough for thev plunger saidplunger having a passage opening communication between the first namedchamber and the second named chamber when the plunger is in itswithdrawn position, a cylinder with a bore of smaller diameter than thesmaller chamber located beyond the smaller chamber, with a fixed headseparating the two smaller chambers, a second plunger connected with therst named plunger and guided through the second named fixed head intothe smallest chamber, said rst named chamber cooperating with itsplunger to force a portion of the operating fluid through the passageinto the second named chamber at the commencement only of the forwardstroke of the plunger, 'and connections from the two smaller chambersfor delivering fluid under pressure from the same.

l 9. In fluid pressure apparatus, the combination 1m of a cylinderhaving a booster chamber of relatively large diameter and a chamber ofrelatively smaller diameter, a plunger with a piston head filling thebooster chamber, a fixed head separating the larger chamber from thesmaller chamber and having a guide opening therethrough for the plunger,a cylinder with a bore of smaller diameter than the smaller chamberlocated beyond the smaller chamber, with a lixed head separating the twosmaller chambers, means 110 cooperating with the booster chamber to passoperating fluid from the booster chamber at the commencement of theforward stroke, into the said second named chamber, a second plungerconnected with the rst named plunger and 116 guided through the secondnamed xed head into the smallest chamber', connections from the twosmaller chambers for delivering lluid under pressure from the same,andmeans for supplying liuid under pressure to all the bores.

10. In a fluid pressure apparatus, the combination of a cylinder havinga bore of relatively large diameter, and a second bore of relativelysmaller diameter, a plunger with a piston head filling the larger bore,a fixed head separating the larger bore from thesecond bore and having aguide opening therethrough for the plunger, means for supplyingoperating fluid to the two bores, a connection from the smaller bore fordelivering fluid under pressure from the same, a third bore of 1msmaller diameter than the second bore located beyond the same, with afixed head separating the two smaller bores, a second plunger guidedthrough the last named head and connected with the first named plungerso as to advance with the first named plunger, a connection leading fromthe third bore for delivering fluid under pressure from the same, meansfor advancing the plungers to develop pressure in the bores, means forreturning the plungers and for normally holding the same in a Withdrawnposition, means for opening communication between the first bore and thesecond bore when the plungers are in their withdrawn position, and meansfor supplying the operating fluid to the third bore when 145 theplungers are in said withdrawn position.

11. In 'a fluid pressure apparatus, the combinationof a cylinder havinga bore of relatively large diameter, and a second bore'of relativelysma1lerdiameter, a plunger with a piston head 150 filling the largerbore, a fixed head separating the larger bore from the second bore andhaving a guide opening therethrough for the plunger, means for supplyingoperating uid to the two bores, a connection from the smaller bore fordelivering fluid under pressure from the same, a third bore of smallerdiameter than the second bore located beyond the same, with a fixed headseparating the two smaller bores, a second plunger guided through thelast named head and connected with the nrst named plunger so as toa'dvance with the rst named plunger, a connection leading from the thirdbore for delivering lluid under pressure from the same, means foradvancing the plungers to develop pressure in the bores, means forreturning the plungers and for normally holding the same in a withdrawnposition, said first named plunger having a port opening communicationbetween the rst charnber or bore and the second chamber or bore when theplungers are in their withdrawn position, and operating to close afterthe plungers have advanced through a part of their forward movement, toenable pressure to be developed in the second c bore, said secondplunger having a port with means communicating with the same to supplythe operating liuid to the third bore when the plungers are in saidwithdrawn position, and operating to close when the plungers haveadvanced through part of their forward movement,l

to develop pressure in the third bore.

l2. in a fluid pressure apparatus, the combination of a cylinder havinga bore of relatively large diameter, and a second bore of relatively 1smaller diameter, a plunger with a piston head nlling the larger bore, afixed head separating the larger bore from the second bore and having aguide opening therethrough for the plunger, means for supplyingoperating fluid to the two bores, a connection from the smaller bore lordelivering huid under pressure from the same, a third bore of smallerdiameter than the second bore located beyond the same, with a fixed headseparating the two smaller bores, a second plunger guided through thelast named head and connected with the rlrst named plunger so as toadvance with the first named plunger, a ccnnection leading from thethird bore for delivering fluid under pressure from the same, means foradvancing the plungers to develop pressure in the bores, means forreturning the plungers and for normally holding the same in a withdrawnposition, means for opening communication between the first bore and thesecond bore .when the plungers are in their withdrawn position, andmeans for supplying the operating huid to the third bore when theplungers are in said withdrawn position, the said connection between theplungers including yielding means permittingI a greater forwardmovement` of the rst plunger than the second plunger when the same moveforwardly, operating to develop a relatively lower pressure in the thirdbore than in the second bore.

i3. In fluid pressure apparatus, the combination of a cylinder having abooster chamber with a bore ol relatively large diameter and a secondbore of relatively smaller diameter, a plunger with a piston headfilling the larger bore, a xed head separating the larger bore from thesmaller bore, and having a guide opening therethrough for the plunger, athird bore disposed beyond the second bore, a second plunger connectedwith the rst plunger and operating to develop pressure in the thirdbore, a prSS/lllt reservoir, means for supplying the operating fluidtherefrom to the rst bore and the third bore, and

eans for enabling the fluid under pressure in the booster chamber to owinto the second named bore at the commencement of the forward stroke.

le. In fluid pressure apparatus, the combination of a cylinder having achamber of relatively iarge diameter and a chamber of relatively smallerdiameter, a plunger with a piston head filling the bore of the largerchamber, a

V'hired head separating the larger chamber from the smaller chamber andhaving a guide opening therethrough for the plunger, a third bore beyondthe second bore with a head between the same, a second plunger guidedthrough the last named head and connected with the first plunger toadvance therewith, a pressure reservoir for the operating iiuid, meansconnecting the reservoir with the nrst chamber or bore, means connectingthe reservoir with the second named fixed head, means for advancing theplungers, means for returning the plungers and for holding the samenormally in a withdrawn position, said first named plunger having a portopening communication between the rst chamber or bore and the secondchamber or bore when the plungers are in the said withdrawn position,said second plunger having a port opening communication between thereservoir and the third bore when the plungers are in their saidwithdrawn position, a connection from the second chamber or bore forsupplying fluid under pressure from the same, and a connection from thethird bore for supplying fluid under pressure from the same.

l5. ln a uid pressure brake apparatus for an automobile, the combinationof a cylinder having a chamber of relatively large diameter and chamberof relatively smaller diameter, a plunger with a piston head filling thelarger chamber, a xed head separating the larger chamber from thesmaller chamber and having a guide opening therethrough for the plunger,a third chamber beyond the second chamber with a head be- LUL tween thesecond and third chambers, a second plunger guided through the lastnamed head and connected with the rst plunger to advance therewith, apressure reservoir for the operating fluid, means connecting thereservoir with the iirst chamber, means connecting the reservoir with152,5

having a port opening communication between" the first chamber and thesecond chamber when the plungers are in the said withdrawn position,said second plunger having a port opening communication between thereservoir and the third chamber when the plungers are in their said185withdrawn position, a connection `from the second chamber for supplyingiluid under pressure to the rear brakes, and a connection from the thirdchamber for supplying fluid under pressure to the forward brakes.

le. En a fluid pressure brake apparatus for an automobile, thecombination of a cylinder having a chamber of relatively large diameterand a chamber ci. relatively smaller diameter, a plunger with a pistonhead filling the larger chamber, a xed head separating the largerchamber from the smaller chamber and having a guide opening therethroughfor the plunger, a third chamber beyondI the second chamber with a headbetween the second and third chambers.

a second plunger guided through the last named head and connected withthe rst plunger to advance therewith, a pressure reservoir for theoperating fluid, means connecting the reservoir with the rst chamber,means connecting the reservoir with the second named xed head, means foradvancing the plungers, means for returning the plungers and for holdingthe same normally in a withdrawn position, said first named plungerhaving a port opening communication between the rst chamber and thesecond chamber when the plungers are in the said withdrawn position,said second plunger having a port opening communication between thereservoir and the third chamber when the plungers are in their Isaidwithdrawn position, a connection from the Sil second chamber forsupplying fluid under pressure to the rear brakes, and a` connectionfrom the third `chamber for supplying fluid under pressure to theforward brakes, the connection between the first plunger and the secondplunger including a spring operating to yield when the plungers areadvanced and thereby develop lower pressure in the fluid serving theforward brakes than in the uid serving the rear brakes.

17. In fluid pressure apparatus, the combination of a cylinder having achamber therein, a head closing the chamber at one end, a plunger guidedto slide through lthe head out of contact with the wall of the chamber,operating to develop pressure within the chamber when the plungeradvances, and means for packing the plunger where it passes through thehead, said plunger having a passage in its side face leading to saidchamber and said head having a passage communicating with the space inthe rear of said'V head and registering with the first named passagewhen the plunger is in its withdrawn position so as to opencommunication from the said chamber into the space in rear of said head.

18. In a liuid-actuated brake, the combination of a brake cylinderhaving a chamber within the same for the actuating uid, a headdetachably secured to said cylinder at the outer end of said chamber,said cylinder having a relatively large bore, a plunger guided in saidbore with its inner end out of contact with the wall of said chamber,means for packing the plunger at said head,

and means for connecting the forward end of the cylinder to the brake,said plunger having a passage in its side face leading to saidconnecting means and said head having a passage communicating with thefirst named passage when the plunger is in its withdrawn position andcommunicating at all times with said chamber so as to open communicationfrom said chamber toy said brake.

19. In a fluid actuated brake controlled by a pedal the combination ofwheel brakes, a master cylinder having a chamber within the same adaptedto contain actuating uid, a head detachably secured within the cylinderat one end of the chamber and formed with an opening, a head detachablysecured within the Vcylinder at the other end of the chamber and formedwith an opening, a plunger corresponding to the opening in the firstnamed head and carried through the same and having a smaller diameterthan the chamber so that the plunger` is out of contact with the Wall,the chamber of a plunger lcorresponding to the opening in the secondhead and carried through the same and having a smaller diameter than thechamber so that the plunger is out of contact with the wall of thechamber, means for connecting a portion of the cylinder forward of onehead with some of said wheel brakes, means for connecting a portion ofthe cylinder forward of .the other head with others of the wheel brakes,and means for operating the plungers by the controlling'pedal, each headbeing formed with a port through which liquid may at times pass, andeach plunger being formed with a port through which liquid may also attimes pass and which at times communicates with the portv in itsassociated head, one of said ports associated with each head andIplunger leading rearward from said head and the other openingassociated with said head and. plunger leading forward of said head. v,

20. In hydraulic brake apparatus, a cylinder, an annular head in saidcylinder secured in fluid tight relationship with the sides thereof, aexible packing associated with said head, and al cylindrical plungerformed with a central recess and a port adapted atv times toallowpliquid .to flow around said annular head, mounted for movement inuid tight relationship through said head and packing.

2l. In fluid pressure apparatus, the combination of a cylinder 'having acompression chamber and having a booster chamber, a plunger having ahead moving in the booster chamber, said cylinder having a by-passconnection from the interior of the booster chamber into the compressionchamber, said by-pass being open when the plunger is in its normalwithdrawn position, and a reservoir for the operating'uid having aconnection with a restricted passage leading into the booster cylinder,said restricted passage operating to choke the outlet from the boosterchamber to the reservoir when the plunger is actuated and therebydevelop pressure in the booster chamber. 22. In fluid pressureapparatus, the combination of a cylinder having a compression chamberand having a booster chamber, a plunger having a head moving in thebooster chamber, said cylinder having a bypass connection from theinterior of the booster chamber into the compression chamber, saidby-pass being-open when the plunger is in its normal withdrawn position,a reservoir for the operating fluid having a connection with arestricted passage leading into the booster cylinder, operating to chokethe outlet from the booster chamber to the reservoir WhenI the plungeris actuated, and thereby develop l] pressure in the booster chamber, thehead of said plunger having a cup packing ring operating to admit airinto the booster chamber on the return movement of the plunger andthereby operating to admit air into the upper end of the reservoir anddevelop pressure in the same.

23. In hydraulic brake apparatus, a cylinder, a head in said cylinderformed with an opening and dividing said cylinder into a rearcompartment and a forward compartment, a flexible Ymounted forreciprocation through the opening yin said head and provided with aport, said head being formed with a groove for at times cooperating withsaid plunger port for affording communication between said forwardchamber and said rear chamber, and a flexible packing lassociated withsaid head.

25. In fluid pressure apparatus, a cylinder, a head formed with anopening and positioned in said cylinder and dividing it into a forwardchamber and a rear chamber, and a plunger slidably mounted forreciprocation through the opening in said head, said plunger beingformed with a passageway, and said head being formed with a port attimes registering with said passage-way for affording communicationbetween said forward chamber and said rear chamber.

26. In hydraulic brake apparatus, a cylinder, an annular head securedwithin said cylinder in uid tight relationship with the sides thereof, acylindrical plunger slidably passing through said annular head andformed with a recess at the forward end thereof, and a packing cupsecured to the forward side of said head and contacting in fluid tightsealing relationship with said plunger, coacting passages being formedthrough said head and through said plunger for allowing communicationbetween the portion of the cylinder in rear of said head and the portionof the cylinder in front of said head when said plunger is in its normalretracted position.

27. In hydraulic brake apparatus, a master' cylinder having an annularhead positioned therein, a cylindrical plunger slidably mounted forreciprocation through said head, an annular packing secured to said headfor at times preventing the passage of ud rearwardly past said head, andan annular packing secured to said plunger adjacent the rear end thereofand contacting with the walls of said cylinder for preventing thepassage of uid rearwardly by said plunger packing, said plunger beingformed with a recess extending rearwardly from the front end thereof andwith a lateral passage extending through the walls of said plunger sopositioned that when the plunger is in its normal rearward positionthepassage is just rearward of said first named' packing.

28. In hydraulic brake apparatus a master cylinder having anannular headpositioned therein forming a pressure creating chamber in advancethereof, an annular packing secured to said head for at times preventingthe passage of fluid rear-V wardly past said head, a cylindrical solidplunger having its forward portion slidablyv mounted for reciprocationthrough said head and packing for creating a brake applying pressure insaid chamber ahead of said packing, and an annular packing secured tosaid plunger at its rearward portion, slidably contacting with the wallsofthe cylinder and coacting with said rearward portion of the plungerfor preventing the passage rearwardly of fluid past the rearward end ofthe plunger.

29. In hydraulic brake apparatus, rear brakes,

front brakes, an annular head formed with a bore and positioned in saidmaster cylinder for dividing it into a pair of chambers one of which isconnected to the forward brakes and one of which is connected to therear brakes, a liquid supply reservoir, a fluid connection leading fromsaid supply reservoir to said bore in said head, and means comprising apair of opposed packing secured on opposite sides of said head forpreventing passage of uid to said bore from said chambers while allowingthe passage of iuid from said bore to said chambers.

30. In a fluid actuated brake apparatus for operating brake cylinders,the combination of a master cylinder having a compression chamber, andhaving a booster chamber with a head between the said chambers, meanscomprising a plunger guided to slide through the said head andconstantly in contact with said head for developing pressure in thebooster chamber and in the compression chamber, means for connecting thecompression chamber to the brake cylinders, and a packing ring forpacking the plunger at the head and operating to permit the liquid underpressure in the booster chamber to iiow past it into the compressionchamber When the plunger is advanced to apply the brakes.

31. In a fluid actuated brake apparatus for operating brake cylinders incombination, a master cylinder having a compression chamber for theiiuid and having a booster chamber and a head separating said chambers,means comprising a plunger guided to slide through said head fordeveloping pressure in the compression chamber, means for holding theplunger normally in afretracted position with the forward end of theplunger lying in the compression chamber, and a reservoir connected withthe booster chamber for maintaining a booster pressure, said head havinga passage therein communicating with the booster chamber, and said'plunger having a port communicating with the passage when the plunger isin its retracted position for opening communication between the boosterchamber and the compression chamber.

32. In a fluid actuated brake apparatus for operating brake cylinders incombination, a master cylinder having a compression chamber and having abooster chamber, a head between said chambers, means comprising aplunger guided to slide through said head for developing pressure in thebooster chamber and in the compression chamber, means for connecting thecompression chamber to the brake cylinders, and a packing ring forpacking the plunger at the head and operating to permit the liquid underpressure in the booster chamber to flow past it into the compressionchamber when theplunger is advanced tol apply the brakes.

EUGENE G. CARROLL.

Sil

Patent No. 1.943, 886.

`ctaltrmlcart; or CORRECTION.

I January 16, 1934.

EUGENE G. CARROLL.

ft is hereby certified that error appears in the printed specificationof the 'the above numbered patent requiring correction as follows: Page7, line 70, claim 19, for the chamber of" read of the chamber,; and thatthe said Letters Patent/(should be read with this correction thereinthat the same may conform tothe record-of the case in the Patent Office.

Signed and sealed this 19th day of March, A. D. i935.

Leslie Frazer (Seal) Acting Commissioner oi Patents

